For the production of urea and carbon dioxide in a urea plant, such a plant may comprise a high pressure stripper, a high pressure carbamate condenser, pool condenser or pool reactor. Such a pool condenser or pool reactor may be of the shell and tube type comprising substantially u-shaped tube bundles extending through a tube sheet. Such a urea plant is for instance described in WO 2009/141346. The shell side of the known pool reactor or pool condenser is filled with high pressure process medium. The U-shaped tube bundle provided in the reactor or condenser is filled with steam condensate for generating low pressure steam. Since a high pressure difference between the shell side and the tube side is present, the tube sheet has to be designed strong enough to withstand the pressure difference between both sides. Besides, for manufacturing of such a pool reactor or pool condenser, each U-shaped tube of the bundle has to be connected to the tube sheet of the reactor or condenser. Due to the U-shape of the tube, connecting of each tube to the tube sheet comprises a difficult and time consuming operation which makes the reactor or condenser difficult to construct. All the more since each U-shaped tube bundle comprises multiple tubes, for instance approximately 500 to 5000, preferably 1000-4000, more preferably 1500-3000 tubes. Consequently, due to the difficult construction, manufacturing costs of such pool reactor or pool condenser are high.
Therefore, it is an object of the present invention to provide an improved method for manufacturing of such pool reactor or pool condenser for use in a urea plant to produce urea. More in particular an object of the invention is to provide a method for manufacturing a tube sheet and heat exchanger assembly for such pool reactor or pool condenser that enables connection of the respective tubes to the tube sheet in an efficient manner.